[Buildroot] [RFC 1/2] busybox: avoid conflict with other packages

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2017-12-29 10:42 +0100, Thomas Petazzoni spake thusly:
> On Fri, 29 Dec 2017 10:38:18 +0100, Yann E. MORIN wrote:
> > As was discussed during the DevDays in Pragues about top-level parallel
> > build, we've concluded that we could not have two packages that touch
> > the same file.
> > 
> > When we are doing top-level parallel build, we no longer have any
> > guarantee of the ordering, especially the order packages install in
> > target/, so we loose the reproducibility that sequentiallity currently
> > provides.
> > 
> > So we have to ensure proper install ordering, so that we guarantee what
> > files are in target/.
> > 
> > So we either go with the current dependencies, added to all packages to
> > ensure they get installed after busybox, or we add them to busybox so it
> > gets installed after all the packages for which it may provide applets.
> > 
> > I prefer the second option, because it concentrates the dependency chain
> > in a single package, and it becomes very easy to write:
> > 
> >     BUSYBOX_DEPENDENCIES = \
> >         $(if $(BR2_PACKAGE_COREUTILS),coreutils) \
> >         $(if $(BR2_PACKAGE_UTIL_LINUX),util-linux) \
> >     [...]
> > 
> > Rather than duplicate the optional dependency on Busybox in all the
> > packages (and as Thomas demonstrated, there are quite a few of them).
> 
> Seems like a good idea to me.

For that, we'll need the three-patch series I submitted to Busybox:
    http://lists.busybox.net/pipermail/busybox/2017-December/086039.html

> > I may even go further: we could even make busybox depend on *all*
> > packages, irrespective on whether it provides applets for them or not,
> > since busybiox is pretty fast to build and does build in parallel quite
> > nicely anyway. That would nicely solve the issue.
> 
> I don't really like this approach, I find it too brutal.

Sorry, I was not advocating for this solution. What I meant was that, to
simplify things even further we could do that. But I don't think we need
that.

> Since we have the testing logic to validate that no package overwrites
> files from another package, I think the approach of having explicit
> dependencies in Busybox is good enough.

Once we turn the warniong into a hard error, yes. ;-)

Regards,
Yann E. MORIN.

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